Update 21/01/15: Microsoft have confirmed that no Mojang.net service was compromised
According to German reports, a list of 1,800 Minecraft usernames and passwords, apparently belonging to German gamers, has been dumped on Pastebin. Heise has verified some login details as valid.
It’s not yet clear how criminals have managed to steal so many credentials, nor if they have any more, but it is likely that a phishing attack to blame for the breach. If the breach is a result of a successful cyber attack on Minecraft itself then there could be bigger problems: Minecraft has some 100 million registered users.
If you’re concerned about your Minecraft account, you should change your password immediately.
More importantly, make sure that none of your other online accounts share the same login credentials.